This invention relates to a spectrophotometer, and more particularly, to an apparatus for automatic initialization of the wavelength indexing function of the diffraction grating of a spectrophotometer.
The accuracy and value of information gained from the utilization of a spectrophotometer are dependent upon initialization of the wavelength indexing function of the diffraction grating. In the past, automatic initialization has been accomplished with an apparatus having dual optical sensors and dual gear trains. Coarse positioning has been provided by one optical sensor and one gear train; fine positioning has been provided by the other sensor and gear train. While this apparatus has performed satisfactorily, precise control of the gear trains in response to the sensors has been necessary. Further, the two gear trains have required a slip clutch for independent, driving engagement with the diffraction and grating frequent calibration has been essential. Still further, an elaborate control mechanism has been necessary for automatic initialization after an abortive use of the spectrophotometer has left the grating in a non-normal ending position.